1. Field of the Disclosure
The present disclosure relates to a bidirectional packet transfer fail-over switch for serial communication , and particularly, to a bidirectional packet transfer fail-over switch for serial communication, which multiplexes a single communication line into a plurality of communication lines in a serial communication network depending on the high-speed transfer of a communication packet and introduction of a bidirectional communication scheme, and transfers and processes bidirectional communication packets which are simultaneously generated.
2. Background of the Disclosure
A communication terminal apparatus of an industrial real-time monitoring and control system is operated in a communication node dualization scheme and a network line dualization scheme, for considering a reliability of a system.
However, in a main unit system, when a distance between communication terminal apparatuses is a long distance of several km or more, the double establishment of a network line causes an increase in the line establishment cost and the operating cost.
Therefore, it is required to establish a single communication line between a main apparatus and a communication terminal apparatus. In the communication terminal apparatus, it is required to operate an efficient dualization system by providing a communication network multiplexing function to a system which is provided as a dualization system.
A serial fail-over switch distributes a communication packet, which is received through a single communication line, to a plurality of network nodes. A system is mostly operated as a unidirectional communication system in which a system main apparatus, a master, is an initial command requester.
A related art fail-over switch for serial communication is implemented to be suitable for a function of transferring a unidirectional communication packet generated from a node in which a master is uniquely defined.
Therefore, signals which are simultaneously generated from two or more nodes are not normally transferred. For example, there is a limitation in characteristic of an operation of transferring packets which are generated from two or more of three nodes at the same time.
A 1:1 communication line between nodes should be established and operated in order for a bidirectional packet to be transferred like a system having a multi-master or an inter-node 1:1 full duplex scheme. However, in long-distance communication, the establishment cost and the operating cost should be expended by two or more times for establishing a plurality of 1:1 communication lines.
In most of monitoring and control systems, a first node is used as a main apparatus node, and a second node and a third node are used as dualization main/auxiliary nodes of a communication terminal apparatus. When there is no response packet in the main node or an error occurs in the main node, the auxiliary node automatically acquires an operation authority, and executes an authority of the main node.
However, the frequent occurrence of collision between communication packets causes a problem in which a normal operation of an operation authority algorithm of the main/auxiliary node is not ensured, causing a reduction in stability of a system.
Recently, as propagation of Ethernet communication is expanded and the requirement for popularization of a medium and a connection with another network increases, communication packet switch equipment is widely propagated and spread in a system terminal apparatus. Also, as the high-speed transfer of a communication packet and introduction of a bidirectional communication scheme are expanded, it is required to introduce a system using a bidirectional switch function even in a serial communication network.